... s Frobenius ln hn 25 N = Arf (1), g = -1 Arf (2,3), g=1 Arf (3,4), Arf (2,5) g=2 g=3 Arf (4,5), Arf (3,5), Arf (2,7), g=4 g=3 g=5 Arf (5,6), Arf (4,6,7), Arf (3,7), Arf (2,9), g=4 g=5 g=7 g=5 ... Sk l mt na nhúm s Arf v S k Arf (S), v vỡ Arf (S) l na nhúm s nh nht cha S, nờn Sk = Arf (S) chng minh rng h Arf cỏc phn t sinh ti tiu l nht, trc ht cn chng minh rng mi h Arf cỏc phn t sinh ... Arf Khi ú lc lng ca mt mt h sinh Arf ti tiu ca S c gi l hng Arf ( Arf rank) ca S Ký hiu: Arf- rank(S) 21 Gi s S l mt na nhúm s v S = , ú = n gin ta s vit Arf...